Ive been hunting for morels for 20 yrs and I never checked the soil temperature and just last year after reading Michael Kuo's book which is awesome,did I find out about different ways to know when the beginning of the season is upon us.Ive always gone on instinct and it's worked out great with the exception of last year when the season was late about one week in my area.Since then I've been watching the lilac bush,size of leaves on oak tree's and for when the first dandelions go to seed.I'm obsessed with looking for signs.As of yesterday their not up here yet but I predict that they will be by Wednesday.I will be out every day to check and I will have my eye on those dandelions and oak tree's.

I know around here in my area the old timers say it is mushroom time when the dogwood blooms are the size of mouse's ears. That seems to hold fairly true. It is also true with turkey hunting...when the dogwoods are blooming the toms will be looking for hens.

I've used different signs to hunt Mushrooms too. When the dogtooth violets are blooming, oak leaves are the size of squerrel ears, and so on. But I think checking soil temp, and moisture/humidity in your area is probably a good thing to keep track of too.
From what I've seen, the soil has to be between 55-60 degrees for at least 3-5 days.
If you overlay the soil temp map of the US with the mushroom found map, mushrooms show up where the temp has been 60 degrees for at least 3 days.
Of course nature will tell you the same things. Leaf buds won't grow, and flowers won't bloom until soil,air, and water are right. Same with Mushrooms. Happy hunting.

A friend and I hit our early spot and I was amazed to find 18 greys last night. All of them growing out of a light moss cover. Kind of strange. But Im going to hit the early bloomer spots this weekend and recommend everyone does the same. Southern Marion Co. Iowa

When they are out for sure is when lilac bushes bloom but thats just yellows usually they are out before that I look at lilac bushes and the folage on them to know